I often hear this pronunciation.

Problem:
This is a mispronunciation and a misspelling.

Explanation:
Americans have a penchant for pronouncing the letter “t” as if it were the letter “d”.

So it is not surprising that the word “kindergarten” — which ends with T-E-N and literally means “children’s garden” in German — gets pronounced by many Americans as “kindergarden” — which ends with D-E-N.

This mispronunciation is consistent with my “Devolution toward Simpler” linguistic hypothesis.

It is simpler to say “den” than it is to say “ten”.

For fun, I searched Google for each of the following words (with the quotation marks, to avoid variations) and got about the indicated numbers of matches:

• “kindergarten” — 37,300,000 matches
• “kindergarden” — 1,180,000 matches

This tells me that Web authors have spelled the word correctly vs. incorrectly by a ratio of 31.6-to-1, which is very good but not great, especially given more than a million matches for the misspelling.

Solution:
“kindergarten”